Kate, the Duchess of Cambridge, was admitted to the King Edward VII Hospital in central London on Monday suffering from Hyperemesis Gravidarum, very acute morning sickness which causes severe nausea and vomiting.

News of her pregnancy and her hospitalisation has generated a worldwide media frenzy with journalists excitedly reporting any update on her condition along with the facial expressions of William when he arrives and departs.

However, two presenters from the Australian 2Day FM radio station managed to go one step further after calling the hospital pretending to be William's grandmother Queen Elizabeth and his father, the heir-to-the throne Prince Charles.

Despite putting on unconvincing impressions of the royal duo, the presenters were put through to the ward where Kate is being treated and given intimate details about how she was faring.

"She is sleeping at the moment and she has had an uneventful night," a flustered-sounding nurse told the presenters, who called in the early hours of Tuesday morning.

"Sleep is good for her. She's been given some fluids to rehydrate her because she was quite dehydrated when she came in. But she's stable at the moment."

The nurse tells the duo that they would be welcome to come and visit after 9 a.m. when Kate has been "freshened up".

"She hasn't had any retching with me since I've been on duty and she has been sleeping on and off. I think it's difficult sleeping in a strange bed as well."

The Australian radio station issued an apology but said the call had been made with "light-hearted intentions".

"We apologise for any inconvenience caused by the inquiry to Kate's hospital," a spokeswoman for the station said in a statement. "We wish Kate and her family all the best and we're glad to hear she's doing well."

However, the station still put the hoax call story high on the front page of its website, calling it "Biggest Royal Prank Ever".

The two presenters, Mel Greig and Michael Christian, said they were surprised that the call was put through.

"We thought we'd be hung up on as soon as they heard our terrible accents," they said. "We're very sorry if we've caused any issues and we're glad to hear that Kate is doing well."

The hospital said it deeply regretted the incident.

"This was a foolish prank call that we all deplore," John Lofthouse, the hospital's chief executive said in a statement. "We take patient confidentiality extremely seriously and we are now reviewing our telephone protocols."

The prince's office said it would not be commenting on the prank call.